Arash Koocheki; Abdollah Hematian Sourki; Mohammad Elahi; Seyed Mohammad Ali Razavi
Abstract
Introduction: β-glucan is the most important water soluble fiber found in cell wall of some cereals such as barley, oat, wheat and rye, that are composed of β-D-glucoseunits with (1→4) (70%) and (1→3) (30%)anomericbonds(Benito-Román, Alonso, & Cocero, 2013).β-glucan ...
Read More
Introduction: β-glucan is the most important water soluble fiber found in cell wall of some cereals such as barley, oat, wheat and rye, that are composed of β-D-glucoseunits with (1→4) (70%) and (1→3) (30%)anomericbonds(Benito-Román, Alonso, & Cocero, 2013).β-glucan is regarded as a dietary fiber in functional foods. It can act as a hydrocolloid due to its thickening characteristic in aqueous phase and can be used as a stabilizer in some foods such as sauces, salad dressing and ice cream (Dawkins & Nnanna, 1995; Kontogiorgos, Biliaderis, Kiosseoglou, & Doxastakis, 2004; Temelli, 1997; Wood & Webster, 1986). Hull-less barley is a barley variety that has no hard coat around its’ seeds. The content of soluble fiber e.g. β-glucan in hull-less barley is higher than of ordinary barley varieties. Hull-lessbarley cv. Lut is the first commercial hull-less barley in Iran registered in 2013 by SPII(Seed and Plant Improvement Institute). Lut is a kind of spring barley cultivar which is precocious and resistant to lodging. It’s average yield is 6.425 t/ha and it is suitable to cultivation in temperate regions of Iran (SPII, 2013).This type of barley contains about 6% β-glucan and thus is a good source for β-glucan extraction.To date no research has been conducted on properties of β-glucan from this cultivar of barley.Considering high technological properties of β-glucan, the present study was carried out to determine the optimal condition for extraction of β-glucan from hull-lessbarley using hot watermethod to achieve the highest qualitative and best functional properties.Materials and methods: Barley flour was obtained by grinding whole kernels of cv. Lut in a laboratory mill and sieved through a 0.50 mm screen. Prior to the extraction procedure, 50 g of barley flour was suspended in 200 ml of aqueous ethanol (80%, v/v) and stirred under reflux for 3 h to remove most of the lipids and inactivate the endogenous β-glucanases. The liquid phase was separated by vacuum filtration and dried at 40 °C for 12 h. 50 g of dried defatted barley flour was suspended in specified amounts of distilled water (solven:flour ratio = 6:1, 8:1 and 10:1) in a 1000 ml beaker. pH was adjusted to the designed levels (5, 7, and 9) by 0.1 N HCl and 0.1 N NaOH solutions. Extraction procedure carried out at 50±1°C for 30, 60 and 90 minutes. Total β-glucan content was determined by the specific enzymatic method of McClear and Glennie-Holmes (1985) using the mixed linkage β-glucan assay kit (K-BGLU 07/11) supplied by Megazyme International (Wicklow, Ireland). The colour of β-glucan gums was measuredusing a Hunter-Lab Colour Flex 45 spectrophotometer (Hunter Associates Laboratory, Inc., Reston, VA, USA). The L*a*b* (CIELAB space) colour space measurement was used for colour analysis of β-glucan samples. Emulsion stability (ES) against high temperature was determined by heating emulsions in a water bath at 80 °C for 30 min followed by centrifuging at 1200 g for 10 min. For foam stability, ovalbumin was dissolved in distilled water and added to β-glucan solution and then whipped vigorously with a laboratory rotor-stator homogenizer at room temperature. Flow behaviour measurements were done by a Brookfield viscometer. The flow behavior index (n) and consistency coefficient (k) values were obtained by fitting the power law model. All chemicals, reagents and solvents were of analytical grade and obtained either from Sigma-Aldrich Co (Deisenhofen, Germany) or from Merck (Darmstadt, Germany).Results &Discussion: Results showed that the extraction time, solvent: flour ratio and pH had significant effect on extraction yield, purity, foam and emulsion stability, consistency coefficient (k), flow behavior index (n) and colour. Increasing the extraction time had significant effects on β-glucan’s yield and purity and improved the emulsion and foam stabilizing effect of β-glucan. Increasing the pH from 5 to 9 significantly enhanced the purity, consistency coefficient (k), foam and emulsion stability. At higher pH levels, extraction yield, flow behavior index (n) and L* decreased. With increasing solvent:flour ratio, extraction yield, purity, consistency coefficient (k), foam and emulsion stability significantly increased. In contrast, the flow behavior index (n) decreased as a result of increase in solvent: flour ratio. However, solvent: flour ratio had no significant effect on L*, a* and b*. Models presented in this study were highly significant and the correlation coefficients could be used for optimization of ß-glucan extraction from hull-less barley. Considering the importance and desirability of the response variables, the best results were obtained when the extraction time, solvent: flour ratio and pH were 90 min, 10:1 and 7.33 respectively. At the optimal condition, extraction yield, purity, foam stability, emulsion stability, consistency coefficient (k), flow behavior index (n), L*, a* and b* were 4.12%, 69.11%, 86.95%, 88.77%, 1.51 Pa.sn, 0.62, 73.42, 0.81 and 8.72 respectively.
Amin Rangriz; Seyed Ali Mortazavi; Morteza Khomeiri; Soheil Amiri
Abstract
IntroductionTraditional mayonnaise is probably one of the oldest and most widely used sauces in all over the world. Mayonnaise is a product with particular consistency and is classified as a type of oil in water emulsions. Vegetable oil, acetic acid, and egg yolk are main components of mayonnaise. In ...
Read More
IntroductionTraditional mayonnaise is probably one of the oldest and most widely used sauces in all over the world. Mayonnaise is a product with particular consistency and is classified as a type of oil in water emulsions. Vegetable oil, acetic acid, and egg yolk are main components of mayonnaise. In addition, mayonnaise may contain salt, sweeteners, spices, effective flavor materials, preservatives and stabilizers. It must contain at least 78.5 % of total fat and 6 % pureegg yolk. Due tohigh levels of oil present in mayonnaise, continuous usageof this product may result in diseases such as obesity,arteriosclerosis, hypertension and cardiovascular diseases.Therefore, consumers tend to consume low-fat products.Yoghurt is a very useful fermented milk products in terms of lactic acid bacteria that have beneficial effects on human health and Because of the similarity between this productand mayonnaise in terms of rheological properties, Yoghurt have been selected as a fat mimetic in mayonnaise.Therefore, the objective of present study was to investigate the effects of partial fat substitutionby yoghurt on physicochemical, rheological and sensory properties of low fat mayonnaise.Materials and methodsMayonnaise preparationOne kilogram of each mayonnaise sample was prepared.Different recipes of mayonnaise contained yoghurt asfat mimetic (as % of oil and yoghurt) including (49.5 % & 25%), (33% & 50%), (16.5% & 75%). All formulations contained 13 % Egg yolk, 10 % Vinegar, 1 %Mustard, 1 % common salt ,4 % sugar , sodium benzoate 0.07 % , Xanthan gum 0.2%.Mayonnaise preparation procedure was as follows; firstlyegg and vinegar were mixed together and then all otherIngredients(including Yoghurt for the low fatmayonnaise recipes) except oil were added and mixed well. The oil was finally poured insidethe mixer very slowly and homogenized for 1 min. Subsamples (250 g) of mayonnaise were aseptically transferredto sterile 250 ml, Duran glass bottles withpolypropylenescrew caps and left for one-day at 5 °C.Proximate composition analysisMoisture, protein, and ash contents were determined accordingto AOAC (2005) official methods. Fat content wasmeasured by Bligh and Dyer (1959) method, and totalcarbohydrate content was calculated by difference.Rheological measurementsRheological measurements were performed after 24 hstorage using a Brookfield viscometer Model RVDV-IIwith aspindle no.6 at 5 °C and 25 °C. Shear stress data wereplotted versus shear rate for each mayonnaise sample ata range of spindle speed (10–200 rpm). Plots of Lnshear stress versus Ln shear rate (for each sample) werethen used to calculate values including flow behaviorindex (n) andconsistency coefficient (K).Texture analysisMayonnaise samples were stored in refrigerator for 24 huntil texture analysis. The measurements were carriedout using a Brookfield texture analyzer (BrookfieldLFRA texture analyzer model number 4500 texture prolite) equipped with a 38 mm diameter cylindrical probeat 25 °C.The condition of the analysis was as follows; one cyclewas applied, at a constant crosshead velocity of 1 mm/s to asample depth of 30 mm, and then returned. From the resultingforce-time curve, the values for texture attributes, i.e.firmness, adhesiveness, and consistency were obtained usingtexture pro lit software.pH measurement and stability testpH was determined using AOAC standard method at 25 °C. The samples were assessed for the stabilitytest after 24 h storage at 35 °C. Mayonnaise stability wasdetermined after centrifugation (10 min, 2,500 rpm), andwas expressed as the volume of separated phase to the totalemulsion volume.Color measurementMayonnaise samples were measured for color in the L*, a*,b* system using a Lovibond Colorimeter.Sensory analysisAfter 1 day storage Sensory characteristics including appearance,color, odor, texture, taste, and overall acceptabilitywere evaluated by 14 semi-trained panel on 5-point hedonicscale (1 = the least or the lowest; 5 = the most or thehighest).Statistical analysisAll the tests were performed in triplicate. The data collectedwere analyzed by one-way analysis of variance (ANOVA),and significant differences of means were compared usingDuncan test at 5 % significance level using SAS softwareprogram.Results and Discussion: In present study, physicochemical, texture, sensory and rheological properties were evaluated in mayonnaise formulation with dairy-based. Fat was partially substituted by yoghurt at levels of 25, 50 and 75% which were referred respectively as SM1 (25% fat substitution level), SM2 (50% fat substitution level) and SM3 (75% fat substitution level) and the full fat mayonnaise (S) with 66 % oil was used as control sample. Results indicated that low-fat mayonnaise samples had considerably lower energy content compared with control sample, but higher water content than it. In terms of texture, SM3 had lower hardness compared with control sample. The samples exhibited thixotropic and shear thinning behavior through rheological studies and all samples were classified in the group of solid viscoelastic materials because, in all samples, storage modulus was greater than loss modulus. Also, the loss tangent of low-fat mayonnaise samples were higher than the control sample which reflects the tendency of these samples behavior to pseudo-liquid behavior. Results of sensory evaluation demonstrated that SM2 and SM3samples, were more acceptable. It was concluded that yoghurt can be used as a suitable fat replacer in mayonnaise formulation.
Hamed Mahdavian Mehr; Arash Koocheki; Mohebbat Mohebbi
Abstract
Introduction: Batter coating is a new technology to reduce fat content of fried foods. The ingredients and flowproperties of batter are the most important parameters to determine the performance of batter coating and quality of the final product. Among batter additives, proteins can be used as an important ...
Read More
Introduction: Batter coating is a new technology to reduce fat content of fried foods. The ingredients and flowproperties of batter are the most important parameters to determine the performance of batter coating and quality of the final product. Among batter additives, proteins can be used as an important and effective component, because of their emulsifying properties, water absorption, and barrier properties. Previous studies have shown that soya protein isolate (SPI) is a very good hydrophilic protein which could be used to control the viscosity of batter. The batter temperature has direct effect on its flow behavior's properties and has a major impact on the quality of final coated product. Therefore, the aim of the present study was to evaluate the effects of temperature (5, 25 and Cº45) and SPI content (2 and 4%), on flow properties of the batter and quality of deep-fried chicken nuggets. Materials and methods:Raw materials such as fresh chicken breasts, onion, salt, hot pepper, wheat flour, baking powder, and 100% pure sunflower oil were purchased from local markets. SPI (92% protein) were obtained from GolharKhorasanRazavi Company. The batter formulations consisted of wheat flour, salt (1.5% w/w, db), baking powder (0.5% w/w, db) and SPI (2 and 4% w/v, db). For all samples, water/dry mix proportion had always been 5:3. Rheological properties of the batters were carried out using a Bohlin rotational viscometer. For each test, shear rate increased from 0 to 300 s−1, followed by a logarithmically decrease from 300 to 0 s−1. The flow behavior index (n) and consistency coefficient (k) values were computed by fitting the power law model, and time dependency properties of the batters were obtained from the area between the upward and downward curves. Temperature dependency of consistency coefficients were assessed by fitting the Arrhenius model. The batter coating on the chicken substrate was appliedat three temperatures (5, 25 and 45 Cº), and batter pickups (%) were calculated by the weight difference between the chicken nuggets after coating to the weight of chicken nuggets before coating. Coated samples were stored at -18 Cº for two weeks. After thawing, chicken nuggets were fried at 180°C for 3 min in sunflower oil using a programmable deep fat fryer. The influence of SPI concentrations and batter temperature on color and crust adhesion of deep-fat fried chicken nuggets was measured with image processing. In brief, images were taken by a digital camera under controlled conditions, and then analyzed by Image J software. The Percentage of adhesion (CRA), obtained by calculating the ratio of the pixels corresponding to the perimeter of the substrate where coating is adhered to the pixels corresponding to the total perimeter of the substrate. The color of deep-fat fried chicken nuggets were examined in terms of L*, a* and b*values. Oil and moisture content of the chicken nuggets was determined by standard techniques. Results & Discussion: Results showed thatall samples had a shear-thinning behaviour at all batter temperatures (n≥0.539). Power law model was adequately suitable to describe the flow behavior of the batters (R2≥0. 994). The activation energy was between 5.106 to 5.630 (kj/mol).Addition of soy protein isolates into the batter, enhanced the time dependency, whereas, the increase of temperature decreased the hysteresis area. The relative increase in apparent viscosity with increasing SPI might be attributed to the high capacity of SPI to absorb free water. However, decrease in apparent viscosity and time dependency of batters with increasing the temperature could be due to the intermolecular interactions in batter system. An increase in temperature weakens the intermolecular interactions and increases the mobility of macromolecules which reduces the batter resistance to shear force. The batter temperature and formulation had significant effect on the batter pickup. This effect was mainly due to the changes occur on flow properties of batter. Using SPI increased the a* and decreased the L* of the final product. This could be due to the active participation of SPI in the Millard reaction. The data obtained for crust adhesion revealed that the increase in SPI concentration lead to a decrease in batter adhesion to the crust. In other words, the ability of soya proteins to form film during early time of frying reduces the moisture migration from the substrate to oil, which creates a positive pressure in the inner layer of crust and reduces the adhesion. Conclusion: Chicken nuggets coated with batter containing SPI had higher moisture and lower oil content than the control sample. Finally, the change in batter temperature had no significant effect on the crust adhesion and oil and water content in the final product.
